HT or not to HT

Hyperthreading - Hype or Help?

[ByronM]

I have several HT servers running java apps that are fully threaded and never see the "2nd" cpu get used more than .0001 percent or so.

Yet the same app on a dual cpu box uses both cpu's just fine.

Problem with JVM, Kernel or just HT in general?

Does anyone have stability issues with kernels? I couldn't get my machines to boot 2.6.5 - i've heard some better timings and tweaks for 2.6 over 2.4 especially for mysql/rdbms type applications (of which i do alot of) so i'm curious as to what you have seen?

Were migrating to opterons, but i want to know what people have done to make use of existing hyperthreaded architecture in a server environment.

[bakedjake]

JVM

JVM is your issue here, but HT is sort of a joke anyways. Go with dual - it's not cost prohibitive anymore.

HT was meant for desktops.

Were migrating to opterons

Ewww... why?

[ByronM]

Ewww... why?

Because they don't suck :)

Our Sun 20z that runs mysql on a single cpu 240 runs circles around our dual xeon and cost 1/3rd.

I'm getting a few more of the sun 20z's because i can affordably but 16 gigs of memory on these to host the index in ram for quick searches.

[bakedjake]

Sun 20z

Got a link for product info? I'm in the process of buying a DB server (MSSQL). I was going quad Xeon, but would consider alternatives.

[ByronM]

[sun.com...]

Thats the papers there.

BTW, if you join there Java Developer prorgam for 1400 over the next 3 years you get the Java developers stuff, inside help & support AND they give you a free v20z.

Website shows list price, you can get a better deal from VAR or if you call sun directly. To find a dual xeon system that offered me the same size factor, performance and uprgadeability in memory it was going to cost me much more.

[bakedjake]

Thanks for the info, Byron!

[martin]

What about HT in general? I enabled HT on a FreeBSD 4.9 box this morning but it doesn't look like it's performing any better than another one with the same hardware but with HT off.

I don't understand who will run a desktop on Xeons ;-)

[SeanW]

The benefits of hyperthreading vary depending on the nature of what you're trying to run. HT implements two cpus within one core, with shared components. If your applications are CPU bound, ie you're ray tracing, you should see performance similar to a dual CPU system. If the processes are doing a lot of I/O (ie having to hit the shared components), you may not get much more performance over that of a uniprocessor system.

I'm not sure I'd go out of my way to get a HT CPU, we've got several here just because the incremental cost was negligible.

Sean

[Macro]

I don't understand who will run a desktop on Xeons ;-)

Music editors using specialists sound editing software, architects using Autocad/3DS max, video editors using Premiere Pro/Liquid Edition/Edius, 3D modellers, power users of applications that are SMP enabled and/or use the extra cache you can get on Xeons.....